1. Field of the Invention
This invention relates to an exhaust gas cleaning system for internal combustion engines, which operates to feed a secondary air to an exhaust port of internal combustion engines, thereby oxidizing and eliminating unburned noxious components such as HC and CO mixed in an exhaust gas flowing therein.
2. Description of the Prior Art
Generally known in such type of exhaust gas cleaning system as comprises connecting a secondary air feed system through to an exhaust system of an internal combustion engine, providing a reed valve device midway of the secondary air feed system, introducing an exhaust gas cleaning secondary air into the exhaust system by opening the reed valve device through operation of the internal combustion engine, thereby eliminating unburned noxious components in the exhaust system. Then, the inventors have proposed an improved exhaust gas cleaning system, whereby a secondary air passage between a reed valve device and an exhaust port of an engine proper is shortened in distance by installing the reed valve device on the side of the internal combustion engine proper, thereby allowing the secondary air to flow into the exhaust port with less resistance, and a maintainability is improved for replacing the reed valve itself and an ignition plug of the engine proper and adjusting a tappet.
However, the secondary air passage between the exhaust port and the reed valve device which is excessively shortened may allow a hot exhaust gas to flow to the reed valve device, thus causing another disadvantage to accelerate a deterioration on such member as is weak in heat like a rubber packing in the device.